The Core Defined

Written by: Jeffrey Sergent, DC

This is a debated topic. A fun nerd-fight if you will? I find the difficult part is really defining the core. Many different groups and clinicians have different muscle groups associated with their definition of the core. But I suppose I will define my own opinion of the groups of muscles that define core and why.

Outer core muscle examples

I like to divide the core into 2 parts: the outer core and inner/deep core. The outer core is what most people typically think of the core as: Rectus abdominis (6 pack muscles), obliques (inner and outer), transverse abdominis, quadratus lumborum (QL), latissimus dorsi and erector spinae. This creates the outer shell. For example, if you think of a can of soda, they would be the outer aluminum shell.

The deeper or inner core muscles create the top and bottom of that can. This would be the diaphragm, pelvic floor, multifidus, longus colli and longus capitis (deep neck flexors). I do include neck muscles, dnf, in the core. My reason for this is basically that the spine works as a unit. If the neck is too far out of alignment, then the lower back will be too. To see what I mean try to do this easy exhale technique on yourself: Place your hands on your low back and now protrude, or jut your neck and chin forward.  Feel how the lower back follows, resulting in increased muscle activation down there.

        

Deeper/Inner core muscles

Deeper/Inner core muscles in the neck.

The reason for the distinction of inner and outer core is in the development of performance and rehab. The goal is to be able to create a brace and muscle stiffness that don’t allow the spine to move. This stiffness protects the spine from mechanical stress during lifting, bending, sitting, standing... pretty much everything. If there is inefficiency in the core, then the energy will be displaced from the muscle and stiffness to the only still structure: the spine.

Really the purpose of the core is to create intra abdominal pressure and stiffness. Let's go back to the can analogy. If you had only the outer shell, no top or bottom, you would be able to deform it without much effort. Now add a lid and bottom, the inner core. This creates more rigidity and stiffness, making you put in a little more effort to crush that can. Now imagine increasing the pressure within by carbonating and shaking up the can. This creates an even greater stiffness. At this point that can would be pretty difficult to deform, and unless someone gets thirsty would last quite a bit longer than any of the individual parts of the can on their own.

Photo sources: www.slamdunk.ru, mikescottdpt.com, www.cityedgephysio.com.au

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Dr. Jeffrey Sergent is a certified Clinical Rehab Specialist and Chiropractor. He earned his Bachelor's Degree in 2004 from Michigan State University and his Doctorate Degree from the National University of Health Sciences in 2008. His special interests include Trigger Point Therapy, the Functional Movement System, Developmental Kinesiology, Pain Neuroscience and nutrition for chronic pain. Currently he practices at Goodyear Chiropractic Health Center in Milwaukee, Wisconsin.

Rants From a Chiropractor: Part 2

Written by: Jeffrey Sergent, DC


Low Back Pain and my Personal Struggle

Let's start at the beginning.  The lower back vertebrae, cartilage, ligaments and muscles are beautifully constructed architecture.  My favorite thoughts on the architecture come from one of my favorite researchers, Stu McGill, PhD.  Professor McGill asks a simple question: If you were an engineer how would you create a structure that needs to resist shear, bending and compression? The common sense answer would describe a stiff bonded pole like structure, think cement cylinders that hold up highways and bridges. Well now, that same structure needs to bend and rotate slightly. Engineering would create multi sections that allow for limited motion and say that this concept is crazy to make possible. Our bodies, our low backs in particular, are designed to take compression, resist shear forces, and allow for bending and rotating. This is possible due to the core systems. See my 'Core Defined' article for my definition of the core.

Disc Bulge of 15/s1 centrally.

Now let's go into my personal story of my struggle with low back pain and sciatica (leg pain). How did I manage to do this to myself with my knowledge of the spine and mechanics? The short answer… I got cocky. The thing with intervertebral discs is that we know they fail. They fail from repetitive movement, most notably flexion and rotation. Day in and day out I was showing people what they were doing wrong at home or with their movement. I would stupidly then do my Core exercises and lifting with good form, thinking that would fix the damage I was doing all day. Like I said… cocky. So cocky I thought somehow my discs won't fail like my patients, because I have great trunk stability, good hip mobility and balance. I was wrong and that wrong caused my disc to not only bulge but fragment in.


In the pictures to the left, the top shows a disc bulge of l5/s1 centrally. You can see the nerve, the line coming down from the bulge is the s1.  The bottom is just to the right of center and reveals a fragment, the cloudy part off the 

A fragment.

disc bulge. This fragment is surrounding the nerve root. Due to the bulge and fragmentation I had right leg pain, numbness and weakness without lower back pain.

Disc injuries come in a variety of shapes and sizes. The size and shape do not correlate to the amount of pain or symptoms. This is a great area of discussion in the pain community (a great nerd fest).  The amount of tissue damage does not equal pain. Actually with disc injuries the more significant the bulge the quicker recovery. Sometimes a small bulge can cause severe symptoms, while a large bulge causes less pain and less direct quality of life issues.  This again is a newer concept within spine literature. The hypothesis is that the larger bulges send more signals of immune mediators to start the re-absorption process. 

Going back to my case, I had a moderate bulge with large fragments; this caused severe stenosis, or narrowing of the opening for my nerve. Due to the size and compression being done to my nerve you would think I would have severe back and leg pain. In reality, I had calf pain, cramping in my foot and calf, weakness in the calf and numbness in the lateral (outer) foot.

Below is a good representation of disc herniations and the type of pain they most likely would create.

 

www.necksolutions.com

Citations:

1.J Craniovertebr Junction Spine. 2013 Jan;4(1):16-20. doi: 10.4103/0974-8237.121619.

Clinical correlation of magnetic resonance imaging with symptom complex in prolapsed intervertebral discdisease: A cross-sectional double blind analysis.

Bajpai J, Saini S, Singh R.

2. J Neurosurg Spine. 2013 Dec;19(6):678-87. doi: 10.3171/2013.9.SPINE13349. Epub 2013 Oct 18.

Predictive value of MRI in decision making for disc surgery for sciatica.

el Barzouhi A¹, Vleggeert-Lankamp CL, Lycklama à Nijeholt GJ, Van der Kallen BF, van den Hout WB, Koes BW, Peul WC; Leiden-Hague Spine Intervention Prognostic Study Group.

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Dr. Jeffrey Sergent is a certified Clinical Rehab Specialist and Chiropractor. He earned his Bachelor's Degree in 2004 from Michigan State University and his Doctorate Degree from the National University of Health Sciences in 2008. His special interests include Trigger Point Therapy, the Functional Movement System, Developmental Kinesiology, Pain Neuroscience and nutrition for chronic pain. Currently he practices at Goodyear Chiropractic Health Center in Milwaukee, Wisconsin.